ASTM D7134-05 (2012) PDF

Full title and description

ASTM D7134-05 (reapproved 2012) — Standard Test Method for Molecular Mass Averages and Molecular Mass Distribution of Atactic Polystyrene by Matrix Assisted Laser Desorption/Ionization (MALDI)-Time of Flight (TOF) Mass Spectrometry (MS). This test method specifies the procedure, instrumentation requirements, calibration approach and limitations for determining molecular-mass averages (Mn, Mw) and the molecular-mass distribution (MMD) of linear atactic polystyrene with narrow molecular-mass distribution using MALDI-TOF mass spectrometry.

Abstract

This test method describes the use of MALDI-TOF-MS to determine molecular mass averages and distributions for linear atactic polystyrene in the approximate molecular-mass range 2 000 to 35 000 g·mol−1. The method covers sample preparation (co-crystallization with an organic matrix and appropriate cationizing salt), instrument settings (typical UV laser at ~337 nm), calibration with polymer standards/biopolymers, data collection and processing, and discusses the assumptions and limitations (method is not absolute and is intended for narrow polydispersity samples, typically M/M < 1.2).

General information

• Status: Withdrawn (withdrawal recorded January 25, 2021; no direct replacement).
• Publication date: Original designation D7134-05 — approved April 1, 2005; published June 2005. Reapproved in 2012 (designated D7134-05(2012)).
• Publisher: ASTM International.
• ICS / categories: 83.080.01 — Plastics in general; ASTM Committee D20 (Plastics), Subcommittee D20.70 (Analytical Methods).
• Edition / version: D7134-05 (original 2005), reapproved 2012 (often shown as D7134-05(2012)).
• Number of pages: 7 pages.

Scope

This test method covers determination of molecular-mass averages and molecular-mass distribution for linear atactic polystyrene of narrow MMD using MALDI-TOF mass spectrometry. The recommended molecular-mass measurement range is approximately 2 000 to 35 000 g·mol−1. The method is not absolute: it requires calibration of the mass axis using suitable polymer or biopolymer standards and assumes relative intensity calibration is effectively constant across the narrow MMD (typically valid when polydispersity < 1.2). The standard notes typical instrument components and key limitations where wider distributions or different chemistries may invalidate assumptions.

Key topics and requirements

• MALDI-TOF-MS technique applied to atactic polystyrene (sample/matrix co-crystallization).
• Calibration of the mass axis using polymer/biopolymer standards (method is not absolute without calibration).
• Recommended analyte mass range: ~2 000–35 000 g·mol−1 and requirement for narrow MMD (polydispersity typically < 1.2).
• Sample preparation: organic-acid matrices, addition of cationizing salts (silver or other metal salts) to promote cationization.
• Instrumentation essentials: UV nitrogen laser around 337 nm (typical), flight tube, acceleration grid, detector; considerations for sample introduction and laser energy control.
• Data collection and interpretation guidance: peak assignment, mass-axis calibration, calculation of Mn, Mw and polydispersity from the mass spectrum.
• Limitations and applicability: method intended for linear atactic polystyrene with narrow distribution; not suitable as a universal absolute-mass determination without appropriate standards.

Typical use and users

Used by polymer research laboratories, quality-control and analytical laboratories in plastics and polymer manufacturing, university research groups studying polymerization and molecular-weight control, and instrumentation developers for MALDI-TOF-MS. Typical applications include characterization of polystyrene standards, interlaboratory comparisons, polymer synthesis research and methods development where rapid mass-distribution profiling is needed for narrow-distribution polystyrenes.

Related standards

Referenced and related documents commonly cited within this test method include ASTM D883 (Terminology Relating to Plastics), ASTM D1600 (Terminology/abbreviations for plastics), and E691 (Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method). Users may also consult other ASTM methods and international practices for molecular-weight determination (for example size-exclusion chromatography/SEC methods) when broader or absolute determinations are required.

Keywords

MALDI-TOF-MS, atactic polystyrene, molecular mass, molecular-mass distribution (MMD), Mn, Mw, polydispersity, mass spectrometry, polymer characterization, calibration standards, D7134.

FAQ

Q: What is this standard?

A: ASTM D7134-05(2012) is a test method that specifies how to measure molecular-mass averages and the molecular-mass distribution of linear atactic polystyrene using MALDI-TOF mass spectrometry.

Q: What does it cover?

A: It covers sample preparation (matrix and cationization), instrument components and typical settings, calibration procedures with polymer/biopolymer standards, data collection and calculation of Mn, Mw and polydispersity, and the method’s limitations (not absolute; intended for narrow MMD in ~2 000–35 000 g·mol−1 range).

Q: Who typically uses it?

A: Polymer analysts, QA/QC labs in plastics manufacturing, academic researchers working on polymer synthesis and characterization, and MALDI instrument developers and service laboratories.

Q: Is it current or superseded?

A: The document D7134-05 was originally approved in 2005 and reapproved in 2012 (designated D7134-05(2012)). It was recorded as withdrawn (withdrawal noted January 25, 2021) and is shown as withdrawn with no direct replacement.

Q: Is it part of a series?

A: It is part of ASTM Committee D20 (Plastics) test methods and was developed by Subcommittee D20.70 (Analytical Methods). It sits within the series of ASTM test methods for plastics and polymer characterization but is a standalone test method specific to MALDI-TOF-MS of atactic polystyrene.

Q: What are the key keywords?

A: Key keywords include MALDI-TOF-MS, atactic polystyrene, molecular mass, molecular-mass distribution, Mn, Mw, polydispersity, polymer calibration, and polymer analysis.